The present invention relates generally to orthopaedic fixation devices, and in particular to a fixation system for vertebral bodies.
Operations of spinal conditions occurring in the area of the lumbar or thoracic vertebral column may be carried out using an anterior approach. Such an approach may be beneficial because pathological processes often affect the anterior column of the spine. Access to the spinal cord also may be easier to achieve via anterior rather than posterior surgical approaches. Additionally, decompressing the spinal cord may be accomplished more simply or effectively by using an anterior approach. The mechanics of supporting the anterior column may also provide a superior alternative to posterial lateral fixation or fusion. Further, as fewer muscular, neurological and vascular structures may be damaged during spinal surgery using an anterior techniquexe2x80x94as compared to a posterior approachxe2x80x94patients can benefit from fewer complications and enjoy faster recovery due to less trauma surrounding the surgical site. Accordingly, new and innovative techniques for treating the spine via anterior approach techniques are being developed.
One internal anterior fixation system for the treatment of vertebral burst fractures known from the related art is disclosed in WO 94/06360 to Danek. This fixation system includes an elongated plate having integral superior, inferior and bridge portions. The superior and inferior portions are provided for fixation to corresponding vertebrae with the bridge portion spanning between the portions over the affected vertebra. The superior portion includes a pair of generally parallel elongated slots, each having scallops for receiving bone fixation screws or bolts. The inferior portion includes a pair of openings through which fixation screws or bolts extend. The slots in the superior portion allow for compression or distraction of the intermediate vertebral region. The openings in the inferior portion are oriented at an oblique angle relative to the longitudinal axis of the plate to provide a quadrilateral fixation construct. The bridge portion has a width significantly less than the width of the superior and inferior fixation portions. In certain embodiments of this known fixation system, the two posterior bone screws may be inserted prior to the implantation of the bone plate. After the insertion of the two bone screws, the bone plate is introduced into the patient""s body through a small incision, placed onto the bone screws, and fastened thereon by means of nuts. Once the bone plate has been fixated, the two anterior screws are screwed into the bone plate through corresponding screw holes.
Another fixation system for vertebral bodies which permits contraction or distraction of parts to be connected during an operation is known from EP 0 829 240 to Harms. This known bone plate comprises a first portion having an elongated hole, extending in the longitudinal direction of the intermediate portion and a second portion having bores, and being connectable with the first portion. A screw connecting the two portions is provided and guided through the elongated hole, for connecting the two portions. One of the portions comprises a structured surface, and the other portion comprises a recess for registering therewith. A fixating element is provided for engagement with the structure for locking the relative position of the two portions relative to each other. Due to the elongate holes, the overall length of the plate is variably adjustable.
Additionally, U.S. Pat. No. 5,707,372 discloses a variable length cross-link device which may be affixed to the rods of a dual rod implant apparatus, or to the heads of opposing pedicle screws through which such rods are positioned. The device is capable of assuming variable length and a variable angulation.
Also, U.S. Pat. No. 5,470,333 discloses a system for stabilizing the cervical and the lumbar region of the spine with an anatomically correct curvature.
Despite these developments, a need exists for an anterior fixation system for vertebral bodies that allows manipulation of the vertebrae for correcting malpositions, which includes the possibility of length adjustment over a long distance, and which permits lordosis and kyphosis formation in vivo even after the implant has been placed.
The invention is related to a fixation device for connecting bone portions. The fixation device includes a first plate and a second plate, each plate having a top surface, a bottom surface for contacting bone, and a fixation bore extending from the top surface to the bottom surface. At least one member is telescopically associated with at least one of the plates. The fixation device also includes a releasably lockable joint. The at least one member permits translation of the plates with respect to each other about a translation axis, and the releasably lockable joint permits swivelling of the plates with respect to each other about a swivel axis oriented transverse to the translation axis.
In some embodiments, the releasably lockable joint includes a first clamping member disposed in a sleeve, with the first clamping member being configured and dimensioned to exert a force against the sleeve. The releasably lockable joint may further include a straining member such as a fastener for translating the first clamping member with respect to the sleeve. At least a portion of the sleeve may be resiliently deformable, and each fixation bore may be disposed at an angle of about 60xc2x0 to about 90xc2x0 with respect to the bottom surface. Also, at least a portion of the sleeve and at least a portion of one of the plates may be configured and dimensioned for positive engagement with respect to each other. The sleeve may be disposed in a bore, with the sleeve and bore each having a plurality of teeth for providing positive engagement.
At least one member may be releasably lockable with at least one of the plates. The releasably lockable joint may further include a second clamping member disposed in the sleeve, with the second clamping member being configured and dimensioned to exert a force against the sleeve. The straining member may be associated with the second clamping member to permit translation of the second clamping member with respect to the sleeve, and the straining member may be threadably associated with the first and second clamping members to permit the members to axially translate with respect to each other.
At least one of the clamping members may have a wedge-shape. The first clamping member may include a wedge shape and the sleeve may include a slot configured and dimensioned to positively receive the first clamping member. The first clamping member may mate with a slot disposed in the sleeve. Also, the first clamping member may include a hole and the fastener may be threadably associated with the hole. The fastener may be axially fixed with respect to the sleeve. In some embodiments, the sleeve and the first clamping member have complementary conical portions.
In order to permit rotation of at least one component selected from the first plate, the second plate, and the at least one member about the swivel axis, a recess may be provided for positive engagement with a tool.
The fixation device may further include at least two fixation members, wherein at least one fixation bore in each plate receives a fixation member for coupling the plate to bone. At least one of the fixation members may be selectably angulated with respect to the bottom surface of a plate.
At least one fixation bore may include a spherical portion, and the fixation device may further include at least one fixation member having a head with a spherical portion. The spherical portion of the head may be sized to rest in the spherical portion of the fixation bore to permit angulation of the fixation member in the fixation bore. The spherical portions may be mutually roughened, structured, or toothed, and the head may be slotted and resiliently deformable. The fixation device may further include a straining member for circumferentially deforming the head, and the head may have a threaded inner cone threadably associated with the straining member.
A collet chuck may be provided, including an outer spherical portion, so that the spherical portions of the at least one fixation bore and collet chuck mate to permit angulation of the portions with respect to each other. The collet chuck may further include a through hole for receiving a fixation member. The through hole may have a first taper, the fixation member may have a second taper, and the tapers may be complementary.
The swivel axis may be oriented substantially perpendicular to the bottom surface of at least one of the plates. Further, the releasably lockable joint may include a shaft coupled to one of the plates and one of the at least one member, with the shaft permitting rotation of the plate with respect to the member. At least a portion of the shaft may be configured and dimensioned for positive engagement with at least one of the plate and the member.
The invention also relates to a fixation device for connecting bone portions including: a first plate and a second plate, each plate having a top surface, a bottom surface for contacting bone, and a fixation bore extending from the top surface to the bottom surface; at least one member telescopically and slidably associated with a channel in at least one of the plates; and a releasably lockable joint. The at least one member permits translation of the plates with respect to each other about a translation axis, and the releasably lockable joint permits swivelling of the plates with respect to each other about a swivel axis oriented transverse to the translation axis.
The invention further relates to a fixation device for connecting bone portions including: first and second plates, each plate having a top surface, a bottom surface for contacting bone, and a fixation bore extending from the top surface to the bottom surface; first and second members, each member being telescopically and slidably associated with the first plate; and a joint defining a first axis and including a clamping member disposed in a sleeve. The members permit translation of the plates with respect to each other, the joint permits angulation of one of the plates with respect to at least one of the members about the first axis, and the clamping member is actuable with respect to the sleeve to releasably fix the angulation.